Never before has the diagnostic ultrasound examination been such an integral part of a physician's arsenal. With the expanding technology of medical imaging modalities and medical interventions, the global trend is towards less invasive medical procedures. Therefore, even more emphasis and value have been placed on the precision of pre-interventional diagnostic imaging modalities, including ultrasound.
Historically, a common application of ultrasound has been an ultrasound evaluation of a patient's greater saphenous vein prior to its use as a conduit for arterial surgical reconstruction for lower extremity revascularization in order to salvage a patient's ischemic leg. The ultrasound evaluation is done to save operation time, so the surgeon can avoid making an unnecessarily long incision down the entire length of the patient's leg, which often has non-healing wounds or gangrene present, and so the surgeon can avoid making an incision in the patient's leg only to discover that the desired vein is in a different location, is absent, is duplicated, or is not suitable for use. To determine whether a vein will be suitable, its patency, transverse diameter, quality and location are evaluated by an ultrasound technologist. If the vein is adequate, its course is marked on the patient's skin with a permanent marking pen.
The following procedure is one currently used to preform the ultrasound evaluation and marking of a patient's greater saphenous vein. A diagnostic ultrasound machine, ordinarily with a 7–10 MHZ linear array transducer, is used. The ultrasound technologist visually estimates the center of the face of the transducer and denotes it with a permanent marking pen line directly on the transducer housing. Another technique is to apply a transducer cover to protect the transducer housing and to mark the cover. The medial aspect of the patient's leg is prepped with alcohol to remove gel residues, lotions or oils. Ultrasound gel is applied, and the leg is scanned to track and mark the vein site, generally at two centimeter increments. The technologist visually centers the vein in the middle of the ultrasound screen, which should appear to correspond with the center of the transducer. The technologist slightly tilts the transducer and wipes the gel from the patient's skin beneath the transducer, with a cloth, while maintaining the transducer contact and, hence, position on the skin. The patient is asked to remove the cap from a permanent marking pen and to place it in the technologist's hand. The technologist marks a dot at the approximate site on the skin based on his/her visual estimation of the center of the transducer. The lights in the room are usually turned off throughout the ultrasound examination. Time is allowed for the ink to dry. Ultrasound gel is reapplied, and the area is re-scanned to confirm that the mark corresponds with the target vessel. Frequently, an error in marking is made, and an alcohol swab is used to erase the mark and the marking process is repeated. This tedious and cumbersome procedure is repeated over the entire length of at least one of the patient's legs. Often it is necessary to assess all four of the patient's extremities to find enough vein for a long composite vein bypass graft. Upon completion of the evaluation and marking, the room is re-lit, gel residue is removed, and the dot marks are lightly swabbed with alcohol to remove any residual gel. Generally, a new marker is now used to re-mark the skin and connect the dots. The patient is instructed not to wash off the marks, and the patient may need to re-mark them at home if the surgery is not scheduled for a few days. If a second technologist is available, one technologist will operate the ultrasound transducer and ultrasound machine controls, while the other technologist wipes away the gel and marks the skin.
Obviously, this method of marking the skin is inherently inaccurate, laborious, and unsophisticated for ultrasound technologists, physicians and other ultrasound operators. Numerous other ultrasound-guided skin-marking procedures are also in use, and all of them are equally deficient as the one just described. While ultrasound methods for identifying targets prior to physician intervention are becoming more valuable, with numerous applications, accuracy is lost because of the crude and cumbersome techniques employed for marking the skin above a feature of interest.